This invention relates to a movement detecting circuit for detecting the degree of a movement between image signals representing images.
Generally the movements of images within such picture as of television images are largely divided into the movements within images and the uniform movements of entire images by the parallel movement of the camera. In the case of transmitting, for example, such image, in order to efficiently utilize the transmitting path, the image band is compressed. The part having a local movement of an object within an image is processed as a movement region and the movement in one direction of the entire image is processed as a still region by detecting a movement vector. The band is compressed stronger in the movement region than in the still region in the transmission. Under such background, numerous movement detecting circuits have been devised and utilized.
However, in some case, depending on the uses of the imaging apparatus, the size of the movement quantity may be positively detected without distinguishing the local movement of the image and the movement in one direction of the entire image from each other. For such uses, there are not only a crime preventing apparatus, adapted Y/C separating apparatus and sequential scanning converting apparatus but also an electronic endoscope apparatus used in a medical instrument and displaying an image having as little image movement and color movement as possible as a still picture output.
Recently, with the progress of the solid state imaging device producing technique, the pixels have become so high in the density and the chips have become so small that an endoscope fitted with a solid state imaging device in the tip part or a so-called electronic endoscope apparatus has been developed. Such apparatus has a function of being inserted into a body cavity to observe an inspected part and to record the observed image of the part. Not only the observing capacity but also the quality of the recorded image is so important as to greatly influence the diagnosis of the inspected part. Therefore, in recording, the endoscope operator has stilled patient, has frozen and displayed the image of the inspected part several times, has selected the most desirable picture as a record image and has thus recorded a still image in a monitor image photographing apparatus, video printer or still video floppy apparatus. However, even if the patient is stilled, so long as the living body interior is being observed, the inspected part will move not a little. In order to eliminate the image movement caused by such object movement, the image will have to be frozen several times in some case.
The deterioration of the recorded image by such movement of the object as is mentioned above is different in the generating form in response to the kind of the imaging device and the, imaging system. For example, in case a CCD of a frame transfer type is used as an imaging device, the movement of the object during the exposure period will be produced as a movement of the image. Also, in case a jump scanning is made by using a CCD of an interline type, in addition to the movement of the image caused by the movement of the object during the exposure period, a flicker will be produced by the difference of the image between the fields. In a so-called color frame sequential system wherein an endoscope is fitted with a monochromatic CCD in the tip part so as to be made small in the diameter and the illuminating light is made, for example, R, G and B sequential lights, as the respective time-serially sequentially imaged R, G and B primary color images are synchronized and displayed, a so-called color movement in which the movement of the object is displayed as a color movement will be a problem.
In order to cope with such problem as is mentioned above, there is such movement detecting circuit 1 as is shown, for example, in FIG. 1.
In the detecting circuit 1 shown in FIG. 1, coding means 3a, 3b and 3c provided respectively with input ends 2a, 2b and 2c to which synchronized R, G and B signals are respectively applied n-value, code and output pixel difference signals of respective input signals. The respective n-valued output signals are conceptionally considered to be made by approximating differential outputs of input signals with n kinds of direction vectors. Therefore, if the respective input signals R, G and B are correlated, the direction vectors of the respective signals will coincide or will be similar but, if they are not correlated, the direction vectors will not coincide or will not be similar. Therefore, the respective signals are compared with the above mentioned coded output signals by a comparing means 4 and are further quantified by a quantifying means 5 so that the size of the movement quantity may be detected and a movement detecting signal 9 may be output from an output end 8.
According to this technique, the size of the movement can be detected at a considerable precision in the frame sequential imaging system and simultaneous type imaging system but, in some case, the frame sequential imaging system has been somewhat lower in the precesion.
To explain this point particularly, for example, in a color frame sequential imaging system in which the illuminating light is made R, G and B sequential lights, respective primary color images are obtained time-serially as R0, G0, B0, R1, G1, B1, . . . Rn, Gn, Bn, . . . Here, in case the images to have the movement detected are set to be Gn and Gn+1, the difference of the signals included in the images of Gn and Gn+1 will be predominantly by the movement and the formation of the movement detecting circuit in FIG. 1 will be sufficient. However, here is a problem in the manner of selecting the images to have the movement detected. Even if it is detected that the movement quantity is small between Gn and Gn+1, the movement quantity will not be always small among Gn, Bn, Rn+1 and Gn+1. In the R, G and B color frame sequential imaging system, in the movement detection for obtaining a still picture having little ,color movement, the movement of a series of R, G and B sequential images must be detected. In such case, the images to have the movement detected are considered to be any combination of Rn, Gn and Bn but the difference of the signals included in the respective images will be not only by the movement but also by such elements as the thickness values and bands of the respective primary color images inherently by the object.
In order to detect the movement included in the image, it is a basis to determine the correlation of the informations included in the images to be detected. Therefore, in the case of the color frame sequential imaging system, it will be desirable to exclude the other differences than the variation by the movement.
According to FIG. 1, as the correlation is determined on the basis of a differential signal of the image, the error by the thickness value of the image will be reduced but, as the bands of the respective sequential signals are not positively made to coincide, the non-coincidence of the bands will be left as an error factor.